Field of the Invention
The present invention relates to a light-emitting apparatus.
Description of the Related Art
There is known a color image display apparatus that includes a color liquid crystal panel having a color filter, and a light-emitting apparatus (backlight apparatus) that irradiates the back surface of the color liquid crystal panel with white light. Conventionally, as a light source of the light-emitting apparatus, a fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) has been mainly used. However, in recent years, as the light source of the light-emitting apparatus, alight emitting diode (LED) that is excellent in power consumption, life, color reproducibility, and environmental load has been used.
The light-emitting apparatus that uses the LED as the light source (LED backlight apparatus) has a large number of the LEDs in general. Japanese Patent Application Laid-open No. 2014-44828 discloses the LED backlight apparatus having a plurality of light-emitting blocks. Each light-emitting block has one or more LEDs. In addition, Japanese Patent Application Laid-open No. 2014-44828 discloses that the light emission brightnesses of the plurality of light-emitting blocks are individually controlled.
It is possible to improve the contrast of a display image (an image displayed on a screen) by reducing the light emission brightness of the light-emitting block that irradiates a low-brightness display area of the screen with light or increasing the light emission brightness of the light-emitting block that irradiates a high-brightness display area of the screen with light. The low-brightness display area is an area in which a dark image is displayed, and the high-brightness display area is an area in which a bright image is displayed. Such light emission brightness control of each light-emitting block corresponding to the feature of the image is referred to as “local dimming control”. In addition, the local dimming control that increases the display brightness (the brightness on the screen) of a small area in which a bright image is displayed is referred to as “high dynamic range (HDR) control”. With the HDR control, it is possible to express glare and glitter that couldn't be expressed conventionally.
As the light-emitting apparatus that realizes an improvement in the color purity of light from the light-emitting apparatus, enlargement of the color gamut of the display image, and an improvement in the color reproducibility of the display image, the light-emitting apparatus having a quantum dot is proposed. Japanese Translation of PCT Application No. 2013-544018 discloses the light-emitting apparatus having the LED that emits blue light or ultraviolet light and a quantum dot sheet that converts the light from the LED to white light. The quantum dot sheet is a sheet (film)-like member that has the quantum dot as a phosphor (fluorescent material). Light that causes excitation of the phosphor is referred to as “excitation light”, and light emitted from the phosphor by the excitation is referred to as “fluorescence”. Consequently, light before the conversion by the quantum dot is the excitation light, and light after the conversion by the quantum dot is the fluorescence. The color purity of the fluorescence from the quantum dot is high, and hence it becomes possible to realize, for example, the enlargement of the color gamut of the display image and the improvement in the color reproducibility of the display image by using the quantum dot.
However, not all of the light from the LED is converted to the white light by the quantum dot sheet, and part of the light from the LED passes through the quantum dot sheet without being converted to the white light. Accordingly, in the conventional light-emitting apparatus that uses the quantum dot, not only the white light but also another light (blue light, ultraviolet light, or the like) is emitted from the light-emitting apparatus. It is desirable for only desired light to be emitted from the light-emitting apparatus, and it is not preferable that light different from the desired light is emitted from the light-emitting apparatus. In addition, in the conventional light-emitting apparatus that uses the quantum dot, extraction efficiency of the white light is low, and hence an increase in the power consumption of the light-emitting apparatus and a reduction in the light emission brightness of the light-emitting apparatus occur. The extraction efficiency of the white light is, e.g., the ratio of the white light from the light-emitting apparatus to the light from the LED (the light amount, brightness, or intensity of the light).